1. Field of the Invention
This invention relates to the structure of a flexible printed circuit board which allows for deformation from the band-like shape to a shape suited to be installed over the inner wall of a tubular or convex-polygonal casing.
2. Description of the Related Art
The flexible printed circuit board is so thin and so conformable to any shape as to be snugly installed in a narrow space. Therefore, it has been used in many electrical instruments.
In general, the flexible printed circuit board has ICs, resistors, condensers, or other rigid electrical parts mounted on the surface thereof, and electrically conductive patterns fabricated therein to connect these electrical parts to one another.
In order to put such a flexible printed circuit board into a tubular or polygonal casing, it must be bent. If, in this case, the bending occurs in regions at which the rigid electrical parts lie, the soldered portions connecting the electrical parts to the patterns will eventually be peeled off. This leads to lower the fidelity of performance of the circuit board.
For this reason, it has been the common practice in the art that when the space in which the flexible printed circuit board is to be installed is of annular form as, for example, in the mounting for the photographic lens of camera, a flexible printed circuit board 10 is formed to a doughnut-like or arcuate shape as shown in FIG. 2(A). Thus, it is made freed from later bending in the regions described above.
However, even if the high density assembling technique was employed, it often happened that the given space on the board was not large enough in size to accommodate all the electrical parts. Another drawback was that the electrical part whose width was wider than the width A of the doughnut-shaped board 10 could not be brought into assembly within the lens mounting.
Note FIG. 2(B) is a cross-sectional view taken along line B--B of FIG. 2(A). In these figures, an outer barrel 1 and an inner tubular member 2 holding the photographic lens are concentrically positioned.